Beacon surgery by shaving the mouse, placing it under anesthesia and sterilizing the abdomen and chest at the planned operative site, make a vertical midline incision in the abdomen with a scalpel exposing the peritoneum. Make another vertical midline incision in the peritoneum for insertion of the telemeter. Insert the TER in the right abdomen underneath the peritoneum, leaving only the leads exposed.
So the peritoneum closed subcutaneously implant TER leads such that the negative or white lead is implanted in the upper right chest and the positive or red lead is implanted over the left upper abdomen. Finally close the skin with sutures. Hi, I'm Mark McCauley from the laboratory of Xandr Wearan in the Department of Medicine at Baylor College of Medicine.
Today I'll be showing you a technique for implanting ECG TERs in mice. We use this technique to study changes in heart rate and heart rhythm and mice. So let's get started.
Before inserting an ECG TER into the mouse, it is important to make sure the TER is sterile and in good working order. This is an example of a small animal telemeter from Data Sciences International with a red positive lead and a white negative lead. Each lead has an insulating sheath, two millimeters of exposed wire, and a plastic capped tip, which prevents erosion of the lead through the skin.
New telemetry devices are typically provided in a sterile condition by the manufacturer, but TERs can be reused provided air cleaned using zyme, 1%solution for over four hours. Additionally, use WA OFI O one disinfectant overnight to sterilize the ECG Telemeter. Be sure to wash the disinfectant off with sterile water before implantation into mice.
Check the telemeter leads for integrity of both the conducting wires and the insulating sheath. Turn on the telemetry transmitter using a magnet and test the signal with an AM radio frequency five 30. The signal should be strong and clear and should vary in intensity and pitch based on manipulation of the wires.
Record the model number, the TER serial number, and the ECG calibration value. If applicable, manufacturers often recommend that the TER should be on for 24 hours prior to implantation. Refer to the instruction manual for your specific ter.
To prepare the TER lead, cut the negative or white lead to approximately 3.5 centimeters and the positive or red lead to 2.5 centimeters. These are the optimal lengths per implantation of the negative lead in the right chest and the positive lead in the left abdomen. Next, remove the insulating sheath to expose seven millimeters of wire.
Paint the ends of the metal lead with super glue and then attach lead caps to the metal tips. These caps will avoid skin erosion due to lead placement. Approximately two to three millimeters of the metal wire should be exposed for electrical sensing of the native heart rhythm.
The use of sterile techniques is crucial in the surgery. For implantation of the telemeter, you will need sterile gloves, a sterile drape, and six O proline sutures. All surgical instruments should be sterilized in a glass bead sterilizer heated to 250 degrees Celsius.
These include two pairs of forceps, one pair of blunt ended scissors, a scalpel, and a needle driver. Be sure to sterilize and wash the TER as previously described before. Use to prepare the mouse for surgery.
First anesthetize the animal in an induction box. After confirming by a toe pinch that the mouse is adequately sedated, completely shave the abdomen and chest of the mouse with electric clippers. Re anesthetize the mouse with isof fluorine and then transfer the mouse to a constant flow anesthesia tube.
Place it in the supine position with its head facing away and tail towards you. Tape down the pause of the mouse to the heated surgical table. Use a heating pad to maintain the temperature of the anesthetized animal within a narrow range of 37 plus or minus one degree Celsius.
A rectal probe may be used to monitor the temperature, wipe its abdomen with an alcohol swab to remove shaved hair and to clean the operative field. Apply Betadine with swabs three times to disinfect the abdomen and chest. Apply the sterile drape to the abdomen of the mouse for intraperitoneal toter implantation.
Begin by using a scalpel to create a vertical midline incision of about 2.5 centimeters in length in the skin, overlying the abdomen using blunt tended scissors. Carefully separate skin from underlying connective tissues. Then create a vertical midline incision in the linear elbow, overlying the peritoneum roughly 1.5 centimeters in length.
Additionally, create a small hole in the peritoneum, just cranial to the peritoneal incision, which will serve as an outlet for subcutaneous leads. While performing surgery, keep the surgical site moist, occasionally dripping sterile saline onto the operative site. Insert the TER into the right peritoneal cavity.
Insert forceps into the hole, superior to the TER, and pull both leads up through the lead hole such that they are protruding from the peritoneum. Use continuous six oh proline sutures to close the 1.5 centimeter peritoneal vertical midline incision. To place the ECG leads in the lead two configuration.
The negative lead with the white transparent sheath will be placed in the right thoracic area. First, create a 0.5 centimeter skin incision in the mouse's upper right chest. Next, use the blunt scissors to create a tunnel back to the abdominal incision.
Pull the negative lead through the tunnel and use a six oh prolene suture to anchor the lead to the pectoral muscle. Make sure the suture is on top of the exposed part of the lead and creates a good contact between the exposed metal wire and underlying muscle. Use a second suture proximal to the previous one to immobilize the lead to the muscle.
Close the skin incision using two three proline sutures. The positive lead is placed in the left abdomen below the left diaphragm and below the heart. An additional incision is not necessary here because the site of lead implantation is close to the vertical midline incision.
Use a six oh proline suture to anchor the lead to the underlying abdominal muscle, making sure it has good contact with the tissue. Finally, close the abdominal muscle and skin sequentially with six O proline sutures in layers. Provide the mouse with the appropriate postoperative care as described in our protocol text.
Now we will show some representative results of a normal ECG waveform. The normal ECG from a wild type mouse clearly shows a P wave, which represents atrial depolarization, followed by a QRS wave, which represents ventricular depolarization. Notice that the p and QRS waves are distinct from the small background noise and that each P wave precedes each QRS in a one-to-one ratio.
Notice also that the distance between each R wave called the R to R interval and between each P wave called the sinus cycle length is regular to noting that the mouse is in normal sinus rhythm. So we've just shown you how to implant an ECG TER into a mouse for ambulatory ECG recording. When performing this procedure, it's important to adequately clean the TER before insertion to place the leaves in the appropriate positions, to completely close the abdomen, and finally to give appropriate analgesia to the mouse after the procedure.
So that's it. Thanks for watching and good luck with your experiments.
